Technical Abstract:
The narrow genetic base of cultivated sunflower has been broadened by the infusion of genes from the wild species which have provided a continued source of desirable agronomic traits for improving cultivated sunflower. The genus Helianthus is composed of 51 species (14 annual and 37 perennial), all native to North America. The utility of the sunflower germplasm collection is dependent upon the genetic diversity of each species i.e., the number of accessions per species and their availability for research. Several of wild sunflower species are rare, threatened, or endangered due to their restricted distribution and the encroachment of human activities destroying their habitats. The objective of this research was to collect seeds (> 2,000 seeds per population) from as many populations as possible of Helianthus exilis, H. californicus, H. eggertii, H. schweinitzii, H. verticillatus, H. smithii and H. porteri and make them available for future research for the improvement of cultivated sunflower. The first exploration for H. exilis took place in September, 2002. It covered 4185 km in California from the Coastal Range (Napa County), north to the Oregon border, to the western foothills of the Sierra Nevada Mountains, and south to Tuolumne County. This 12 day exploration trip resulted in the collection of 26 populations of serpentine sunflower with over 2,000 seeds each. The second exploration for perennial California sunflower took place September, 2003 covering 4280 km in central and southern California. This 10 day exploration resulted in the collection of 12 populations of perennial H. californicus with over 2,000 seeds for each population. The last exploration for Eggert's, Schweinitz's, whorled, Smith's and Porter's sunflower was undertaken in October, 2003. It covered 4610 km in the states of Georgia, Tennessee, North and South Carolina, and Alabama. This exploration to the southeastern USA was a 12 day trip. It resulted in the collection of 13 populations of H. eggertii, 14 populations of H. schweinitzii, one populations of H. smithii, two populations of H. verticillatus, and eight populations of H. porteri. None of the five species previously had seed available for research. There are still several gaps in the wild sunflower germplasm collection. Currently 22 species of Helianthus are listed as unavailable since the seed quantity is below the 2,000 seed minimum threshold limit, below which seed distribution stops pending either seed regeneration or recollection. Future explorations will be planned according to the perceived needs of the sunflower community. Assuming one collecting trip per year, it may be possible to collect seed of all remaining 22 species within the next decade.